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Tuesday 6 December 2016

A trio of terrors can hit in late pregnancy

Important to treat symptoms early if ewe and unborn lambs are to survive

Michael Gottstein

Published 01/03/2011 | 05:00

Milk fever, twin lamb disease and grass tetany are the main problems to watch for in the late stages of pregnancy and in lactating ewes at grass.

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Milk fever and twin lamb disease can show almost identical symptoms in ewes prior to lambing.

Milk fever

Milk fever or hypocalcaemia is caused by a lack of calcium in the ewe's diet or her inability to mobilise her own calcium reserves.

Unlike cattle, milk fever is most often seen in sheep before lambing. Affected sheep are dull, refuse to eat and often 'go down'.

The symptoms are almost identical to twin lamb disease and the loss of appetite from milk fever can actually lead the ewe to be affected by twin lamb disease at the same time.

Affected animals should be treated with a suitable calcium gluconate injection (injected under the skin) which should be warmed to body temperature before being administered. The disease can be differentiated from twin lamb disease by the ewe's response to the calcium therapy.

Twin Lamb Disease

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Twin lamb disease, also known as pregnancy toxaemia, is a metabolic disorder which happens when the ewe is short of energy in late pregnancy.

Where a significant number of otherwise healthy sheep are going down, it is a sure sign that feeding levels are inadequate. Lame sheep or shy feeders are particularly at risk and should be penned separately and given plenty of trough space.

Affected ewes appear dull, lethargic, may suffer spasms or tremors and may appear blind. Rapid treatment with a glucose/glycerol-based drench is required if the ewe and her unborn lambs are to be saved.

Grass tetany

Grass Tetany or hypomagnesaemia is a lack of magnesium in the blood supply of lactating animals. Poor weather conditions, grass scarcities and stress can trigger the condition. The condition is compounded by the fact that the uptake of magnesium by the animal is significantly reduced (by a factor of four) when it is stressed.

Affected animals will rapidly enter a coma and die if they are not treated with magnesium. Applying a warm (body temperature) magnesium solution under the skin may be effective when the affected animal is detected early.

On farms where grass tetany is a frequent occurrence, it will pay to put in place measures to prevent the sheep from going down with grass tetany.

Magnesium is not stored in the body for more than a few days. Therefore, for supplementation to be effective it needs to be given on a daily basis during risk periods. The target level of magnesium supplementation is 3-5 grams of magnesium per head per day. Protection will occur 1-2 days after supplementation starts and will last for 1-3 days after supplementation has ceased.

From a practical point of view the main supplementation methods for sheep farmers are:

  • Hi-mag bullets,
  • Mineral licks,
  • Meal containing Cal mag,
  • Pasture dusting.

Water medication which is often used with dairy and suckler cows is not successful in sheep situations.

Farmers should remember that it is important to limit access of male animals to magnesium in order to avoid urinary calculi. There is no safe amount of magnesium that can be fed to male sheep.

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